Under current local Fire and Building Codes, buildings to which the public have access are required to have signage therein identifying the exits. Most of these signs are required to exhibit a specific amount of illumination.
Traditionally, two 15-watt incandescent light bulbs driven by 120 volt alternating current (120 VAC) have been employed to provide normal illumination. Additionally, a pair of 3.6-watt incandescent light bulbs driven by a self contained emergency back-up battery power supply may be provided for illumination during power failure situations.
While these traditional exit sign lighting arrangements perform adequately, they do have a few drawbacks. A major drawback is that the incandescent bulbs use large amounts of electrical power resulting in relatively large operating costs. The 15-watt bulbs generally remain illuminated 24 hours a day, 365 days a year thereby consuming large amounts of power while the emergency 3.6-watt bulbs require a large battery power supply to remain illuminated for the required period of time during power failure situation. Furthermore, while the incandescent bulbs provide adequate illumination, such bulbs do not have a long life in service and require frequent replacement, therefore contributing to the large operational costs associated with inspection and replacement of the bulbs.
To overcome some of the drawbacks associate with high voltage, large power consumption incandescent bulbs, a light device has been developed wherein each high voltage incandescent bulb is replaced by a plurality of series connected, low voltage incandescent lamps. Such a device is shown and described in U.S. Pat. No. 4,782,429.
While the above described device has a longer life in service and reduced energy consumption as compared to high voltage incandescent bulbs, the low voltage incandescent bulbs are still subject to failure, particularly in response to mechanical shock. To alleviate the drawbacks associated with incandescent bulbs, many manufacturers utilize light emitting diodes (LED) rather than incandescent bulbs in exit signs. Each light emitting diode provides a relatively small amount of light as compared to traditional incandescent bulbs, and therefore a large number of light emitting diodes must be used to provide the same amount of illumination offered by traditional incandescent bulbs. For the replacement of incandescent bulbs with light emitting diodes in existing exit signs, special tools, adapters, and other rewiring is typically required.